This project encompasses all statistical coordinating center responsibilities for collaborative clinical studies undertaken by this Section and the Office of the Chief. Current collaborative clinical studies being planned include a double-blind trial designed to examine the influence of anticonvulsant therapy on the natural history of seizure disorders in young patients. Whether treatment after the first seizure can alter likelihood of development of chronic epilepsy is a question often raised with no definitive answer. A number of observational studies establish that many persons who experience a first generalized convulsion do not experience a recurrence during two to five year periods of follow-up. Since prescription of anticonvulsant medication involves risk of side effects as well as expense, it might be desirable to withhold a commitment to chronic therapy until a second or subsequent seizure takes place. It is anticipated that the local clinics in Israel will fund the clinical aspects of the trial and design, establishment and maintenance of the master data file, monitoring and analysis will be the function of BFSB as the statistical coordinating center. A second collaborative study involves the study of the etiology of Parkinson's disease (PD) using the twin Pair registry of the National Academy of Sciences/National Research Council. The prevalent cases of PD in the more than 6,000 twin pairs in which both members are alive, will be identified. This observational study will include: environmental, medical and family histories of both affected and unaffected members of the twin pairs; DNA banking; and measurement of progression of disease over time. This project will investigate genetic and environmental contributions and their interactions to the etiology of PD. A Cooperative Agreement has been submitted for funding of the clinical aspects of this study. BFSB will act as the statistical coordinating center. BFSB will collaborate on the development of the record linkage system of the Kaiser Permanente HMO (with several million members) so that the HMO may be used in the future as a research resource for testing of hypotheses on the etiology and progression of PD.